Breast cancer is the second most common source of brain metastasis. Stereotactic radiosurgery (SRS) can be an effective treatment for some patients with brain metastasis (BM). Necrosis is a common feature of many brain tumors, including BM; however, the influence of tumor necrosis on treatment efficacy of SRS in women with breast cancer metastatic to the brain is unknown.
A cohort of 147 women with breast cancer and BM treated consecutively with SRS over 10 years were studied. Of these, 80 (54.4%) had necrosis identified on pretreatment magnetic resonance images and 67 (46.4%) did not. Survival times were computed using the Kaplan-Meier method. Log-rank tests were used to compare groups with respect to survival times, Cox proportional hazards regression models were used to perform univariate and multivariate analyses, and chi-square and Fisher exact tests were used to compare clinicopathologic covariates.
Neurological survival (NS) and survival after SRS were decreased in BM patients with necrosis at the time of SRS compared with patients without necrosis by 32% and 27%, respectively (NS median survival, 25 vs 17 months [log-rank test, P = .006]; SRS median survival, 15 vs 11 months [log-rank test, P = .045]). On multivariate analysis, HER2 amplification status and necrosis influenced NS and SRS after adjusting for standard clinical features, including BM number, size, and volume as well as Karnofsky performance status.
Neuroimaging evidence of necrosis at the time of SRS significantly diminished the efficacy of therapy and was a potent prognostic marker.